src/chrome/utility/cloud_print/pwg_encoder.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/utility/cloud_print/pwg_encoder.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/big_endian.h"
  10 #include "base/logging.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "chrome/utility/cloud_print/bitmap_image.h"
  13
  14 namespace cloud_print {
  15
  16 namespace {
  17
  18 const uint32 kBitsPerColor = 8;
  19 const uint32 kColorOrder = 0;  // chunky.
  20
  21 // Coefficients used to convert from RGB to monochrome.
  22 const uint32 kRedCoefficient = 2125;
  23 const uint32 kGreenCoefficient = 7154;
  24 const uint32 kBlueCoefficient = 721;
  25 const uint32 kColorCoefficientDenominator = 10000;
  26
  27 const char kPwgKeyword[] = "RaS2";
  28
  29 const uint32 kHeaderSize = 1796;
  30 const uint32 kHeaderCupsDuplex = 272;
  31 const uint32 kHeaderCupsHwResolutionHorizontal = 276;
  32 const uint32 kHeaderCupsHwResolutionVertical = 280;
  33 const uint32 kHeaderCupsTumble = 368;
  34 const uint32 kHeaderCupsWidth = 372;
  35 const uint32 kHeaderCupsHeight = 376;
  36 const uint32 kHeaderCupsBitsPerColor = 384;
  37 const uint32 kHeaderCupsBitsPerPixel = 388;
  38 const uint32 kHeaderCupsBytesPerLine = 392;
  39 const uint32 kHeaderCupsColorOrder = 396;
  40 const uint32 kHeaderCupsColorSpace = 400;
  41 const uint32 kHeaderCupsNumColors = 420;
  42 const uint32 kHeaderPwgTotalPageCount = 452;
  43 const uint32 kHeaderPwgCrossFeedTransform = 456;
  44 const uint32 kHeaderPwgFeedTransform = 460;
  45
  46 const int kPwgMaxPackedRows = 256;
  47
  48 const int kPwgMaxPackedPixels = 128;
  49
  50 struct RGBA8 {
  51   uint8 red;
  52   uint8 green;
  53   uint8 blue;
  54   uint8 alpha;
  55 };
  56
  57 struct BGRA8 {
  58   uint8 blue;
  59   uint8 green;
  60   uint8 red;
  61   uint8 alpha;
  62 };
  63
  64 template <class InputStruct>
  65 inline void encodePixelToRGB(const void* pixel, std::string* output) {
  66   const InputStruct* i = reinterpret_cast<const InputStruct*>(pixel);
  67   output->push_back(static_cast<char>(i->red));
  68   output->push_back(static_cast<char>(i->green));
  69   output->push_back(static_cast<char>(i->blue));
  70 }
  71
  72 template <class InputStruct>
  73 inline void encodePixelToMonochrome(const void* pixel, std::string* output) {
  74   const InputStruct* i = reinterpret_cast<const InputStruct*>(pixel);
  75   output->push_back(static_cast<char>((i->red * kRedCoefficient +
  76                                        i->green * kGreenCoefficient +
  77                                        i->blue * kBlueCoefficient) /
  78                                       kColorCoefficientDenominator));
  79 }
  80
  81 }  // namespace
  82
  83 PwgEncoder::PwgEncoder() {}
  84
  85 void PwgEncoder::EncodeDocumentHeader(std::string* output) const {
  86   output->clear();
  87   output->append(kPwgKeyword, 4);
  88 }
  89
  90 void PwgEncoder::EncodePageHeader(const BitmapImage& image,
  91                                   const PwgHeaderInfo& pwg_header_info,
  92                                   std::string* output) const {
  93   char header[kHeaderSize];
  94   memset(header, 0, kHeaderSize);
  95
  96   uint32 num_colors =
  97       pwg_header_info.color_space == PwgHeaderInfo::SGRAY ? 1 : 3;
  98   uint32 bits_per_pixel = num_colors * kBitsPerColor;
  99
 100   base::WriteBigEndian<uint32>(header + kHeaderCupsDuplex,
 101                                pwg_header_info.duplex ? 1 : 0);
 102   base::WriteBigEndian<uint32>(header + kHeaderCupsHwResolutionHorizontal,
 103                                pwg_header_info.dpi);
 104   base::WriteBigEndian<uint32>(header + kHeaderCupsHwResolutionVertical,
 105                                pwg_header_info.dpi);
 106   base::WriteBigEndian<uint32>(header + kHeaderCupsTumble,
 107                                pwg_header_info.tumble ? 1 : 0);
 108   base::WriteBigEndian<uint32>(header + kHeaderCupsWidth, image.size().width());
 109   base::WriteBigEndian<uint32>(header + kHeaderCupsHeight,
 110                                image.size().height());
 111   base::WriteBigEndian<uint32>(header + kHeaderCupsBitsPerColor, kBitsPerColor);
 112   base::WriteBigEndian<uint32>(header + kHeaderCupsBitsPerPixel,
 113                                bits_per_pixel);
 114   base::WriteBigEndian<uint32>(header + kHeaderCupsBytesPerLine,
 115                                (bits_per_pixel * image.size().width() + 7) / 8);
 116   base::WriteBigEndian<uint32>(header + kHeaderCupsColorOrder, kColorOrder);
 117   base::WriteBigEndian<uint32>(header + kHeaderCupsColorSpace,
 118                                pwg_header_info.color_space);
 119   base::WriteBigEndian<uint32>(header + kHeaderCupsNumColors, num_colors);
 120   base::WriteBigEndian<uint32>(header + kHeaderPwgCrossFeedTransform,
 121                                pwg_header_info.flipx ? -1 : 1);
 122   base::WriteBigEndian<uint32>(header + kHeaderPwgFeedTransform,
 123                                pwg_header_info.flipy ? -1 : 1);
 124   base::WriteBigEndian<uint32>(header + kHeaderPwgTotalPageCount,
 125                                pwg_header_info.total_pages);
 126   output->append(header, kHeaderSize);
 127 }
 128
 129 template <typename InputStruct, class RandomAccessIterator>
 130 void PwgEncoder::EncodeRow(RandomAccessIterator pos,
 131                            RandomAccessIterator row_end,
 132                            bool monochrome,
 133                            std::string* output) const {
 134   // According to PWG-raster, a sequence of N identical pixels (up to 128)
 135   // can be encoded by a byte N-1, followed by the information on
 136   // that pixel. Any generic sequence of N pixels (up to 129) can be encoded
 137   // with (signed) byte 1-N, followed by the information on the N pixels.
 138   // Notice that for sequences of 1 pixel there is no difference between
 139   // the two encodings.
 140
 141   // We encode every largest sequence of identical pixels together because it
 142   // usually saves the most space. Every other pixel should be encoded in the
 143   // smallest number of generic sequences.
 144   // NOTE: the algorithm is not optimal especially in case of monochrome.
 145   while (pos != row_end) {
 146     RandomAccessIterator it = pos + 1;
 147     RandomAccessIterator end = std::min(pos + kPwgMaxPackedPixels, row_end);
 148
 149     // Counts how many identical pixels (up to 128).
 150     while (it != end && *pos == *it) {
 151       ++it;
 152     }
 153     if (it != pos + 1) {  // More than one pixel
 154       output->push_back(static_cast<char>((it - pos) - 1));
 155       if (monochrome)
 156         encodePixelToMonochrome<InputStruct>(&*pos, output);
 157       else
 158         encodePixelToRGB<InputStruct>(&*pos, output);
 159       pos = it;
 160     } else {
 161       // Finds how many pixels there are each different from the previous one.
 162       // IMPORTANT: even if sequences of different pixels can contain as many
 163       // as 129 pixels, we restrict to 128 because some decoders don't manage
 164       // it correctly. So iterating until it != end is correct.
 165       while (it != end && *it != *(it - 1)) {
 166         ++it;
 167       }
 168       // Optimization: ignores the last pixel of the sequence if it is followed
 169       // by an identical pixel, as it is more convenient for it to be the start
 170       // of a new sequence of identical pixels. Notice that we don't compare
 171       // to end, but row_end.
 172       if (it != row_end && *it == *(it - 1)) {
 173         --it;
 174       }
 175       output->push_back(static_cast<char>(1 - (it - pos)));
 176       while (pos != it) {
 177         if (monochrome)
 178           encodePixelToMonochrome<InputStruct>(&*pos, output);
 179         else
 180           encodePixelToRGB<InputStruct>(&*pos, output);
 181         ++pos;
 182       }
 183     }
 184   }
 185 }
 186
 187 inline const uint8* PwgEncoder::GetRow(const BitmapImage& image,
 188                                        int row,
 189                                        bool flipy) const {
 190   return image.GetPixel(
 191       gfx::Point(0, flipy ? image.size().height() - 1 - row : row));
 192 }
 193
 194 // Given a pointer to a struct Image, create a PWG of the image and
 195 // put the compressed image data in the string.  Returns true on success.
 196 // The content of the string is undefined on failure.
 197 bool PwgEncoder::EncodePage(const BitmapImage& image,
 198                             const PwgHeaderInfo& pwg_header_info,
 199                             std::string* output) const {
 200   // pwg_header_info.color_space can only contain color spaces that are
 201   // supported, so no sanity check is needed.
 202   switch (image.colorspace()) {
 203     case BitmapImage::RGBA:
 204       return EncodePageWithColorspace<RGBA8>(image, pwg_header_info, output);
 205
 206     case BitmapImage::BGRA:
 207       return EncodePageWithColorspace<BGRA8>(image, pwg_header_info, output);
 208
 209     default:
 210       LOG(ERROR) << "Unsupported colorspace.";
 211       return false;
 212   }
 213 }
 214
 215 template <typename InputStruct>
 216 bool PwgEncoder::EncodePageWithColorspace(const BitmapImage& image,
 217                                           const PwgHeaderInfo& pwg_header_info,
 218                                           std::string* output) const {
 219   bool monochrome = pwg_header_info.color_space == PwgHeaderInfo::SGRAY;
 220   EncodePageHeader(image, pwg_header_info, output);
 221
 222   // Ensure no integer overflow.
 223   CHECK(image.size().width() < INT_MAX / image.channels());
 224   int row_size = image.size().width() * image.channels();
 225
 226   int row_number = 0;
 227   while (row_number < image.size().height()) {
 228     const uint8* current_row =
 229         GetRow(image, row_number++, pwg_header_info.flipy);
 230     int num_identical_rows = 1;
 231     // We count how many times the current row is repeated.
 232     while (num_identical_rows < kPwgMaxPackedRows &&
 233            row_number < image.size().height() &&
 234            !memcmp(current_row,
 235                    GetRow(image, row_number, pwg_header_info.flipy),
 236                    row_size)) {
 237       num_identical_rows++;
 238       row_number++;
 239     }
 240     output->push_back(static_cast<char>(num_identical_rows - 1));
 241
 242     // Both supported colorspaces have a 32-bit pixels information.
 243     // Converts the list of uint8 to uint32 as every pixels contains 4 bytes
 244     // of information and comparison of elements is easier. The actual
 245     // Management of the bytes of the pixel is done by pixel_encoder function
 246     // on the original array to avoid endian problems.
 247     const uint32* pos = reinterpret_cast<const uint32*>(current_row);
 248     const uint32* row_end = pos + image.size().width();
 249     if (!pwg_header_info.flipx) {
 250       EncodeRow<InputStruct>(pos, row_end, monochrome, output);
 251     } else {
 252       // We reverse the iterators.
 253       EncodeRow<InputStruct>(std::reverse_iterator<const uint32*>(row_end),
 254                              std::reverse_iterator<const uint32*>(pos),
 255                              monochrome,
 256                              output);
 257     }
 258   }
 259   return true;
 260 }
 261
 262 }  // namespace cloud_print